The present invention relates to a nanofiber manufacturing apparatus which produces fibers having diameters of submicron order or nanometer order (referred to as nanofibers in this description) by electrostatic stretching, and a method of manufacturing nanofibers.
There is a known method of manufacturing filamentous (fibrous) substances containing a resin and having a submicron- or nanometer-scale diameter by making use of electrostatic stretching (electrospinning).
The electrostatic stretching is a method of manufacturing nanofibers. In the method, a solution prepared by dispersing or dissolving a solute such as a resin in a solvent is effused (ejected) into space through a nozzle or the like, and the solution is charged and electrically stretched in flight so that nanofibers are produced.
The following describes the electrostatic stretching more specifically. The solvent gradually evaporates from the charged solution while the solution effused into space is in flight. The volume of the solution in flight thus gradually decreases while the charges imparted to the solution stay in the solution. As a result, the charge density of the solution in flight gradually increases. The solvent continuously evaporates and the charge density of the solution further increases, and the solution is explosively stretched into a line when the Coulomb force generated in the solution and repulsive to the surface tension of the solution surpasses the surface tension. This is how the electrostatic stretching occurs. The electrostatic stretching exponentially occurs in space consecutively so that nanofibers having diameters of sub-micron orders or nanometer orders are produced.
In order to manufacture nanofibers by the electrostatic stretching, an apparatus as disclosed in Japanese Unexamined Patent Application Publication Number 2002-201559 is used which includes a nozzle through which a solution is effused into space and an electrode disposed apart from the nozzle. A high voltage is applied between the nozzle and the electrode. The amount of charges of the solution depends on the distance between the nozzle and the electrode and the voltage applied. The amount of evaporation of the solvent contained in the solution depends on the distance between the nozzle and the electrode.